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I have a usb stick witch is encrypted using truecrypt. How can I back it up?

The only method that comes into my mind is making a image of the usb drive and then restore it. But 16 GB I think it will take some long time. Also I want the backup to be encrypted.

Thanks

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closed as off topic by makerofthings7, Gilles, Scott Pack, Iszi, Polynomial Jan 23 '13 at 11:10

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I can't help on on the practical side, but you should not create a binary copy of the encrypted disk(ciphertext). Copy the plaintext into a new encrypted container. –  CodesInChaos Jan 20 '13 at 17:42

3 Answers 3

up vote 2 down vote accepted

Rsyncrypto is a way to minimize backup time for encrypted data but it may not be the perfect solution in this case.

You can have a backup TrueCrypt volume on your machine and automatically sync it with your encrypted USB volume (after it is mounted) using a sync tool like SyncToy.

Or you can backup directly and securely to the cloud by using BoxCryptor. When you mount your encrypted USB drive, Dropbox (for example) will start synching the modified files to the cloud and BoxCryptor will intercept and encrypt the data on the fly.

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Make a binary copy of your usb stick. In linux you can do this with the dd command. This indeed may take a long time, but in your case there is no good alternative unless you make a separate truecrypt volume somewhere and manually copy files from time to time to there.

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This is the best way. The other solutions proposed would have you encrypt the data some other way, which potentially compromises its security (I would prefer to have my data encrypted only in one way; having it encrypted multiple ways gives my adversaries several different targets to pick from). 16 GB of data will not take a long time to copy unless you are using very old technology. I regularly backup 2 TB of encrypted data using dd. –  Tom Marthenal Jan 20 '13 at 7:42
    
Are you recommending a copy of the ciphertext or of the plaintext? The first one is not recommended. –  CodesInChaos Jan 20 '13 at 17:42
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Why wouldn't it be recommended? If you make a binary copy of an the encrypted volume, it still will remain encrypted. –  Lucas Kauffman Jan 20 '13 at 17:57

You must be able to use rdiff backup or rsync on binary image of whole USB stick.

Even encrypted, only few block are modified in fact while normal use.

rdiff (like rsync) will need to read the entire key, but backup storage (and even bandwith if remote backup) will be keeped at raisonable size (static size if rsync ).

Be care to use a key with bigger or equal size than original key to restore your backup! (Having a key with exact equal size will keep you out from stupid problem about automatized virtual hard drive geometry )

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